Fuel Tank Gauge

[morbias]

So the fuel gauge on my 260z goes straight to full when the ignition is turned on, I reckon I have less than a quarter of a tank of fuel and I'm getting a resistance of 11 ohms acrosss the sender contacts which I assume is about right? Not sure of the full resistance range of a working sender unit so if anyone knows off hand that would be a big help!

Looking at the wiring diagram in the FSM it doesn't make sense. Someone please tell me I'm not going crazy and the diagram in the FSM is wrong!

The diagram shows the 'live' yellow wire from the sender going through connector 3 and coming out black & white and going straight to the ignition switch. It also shows the black & white wire from the fuse box going through connector 3 and coming out yellow and going to the gauge.

I'm pretty sure yellow should come out yellow and b/w should come out b/w otherwise the circuit just doesn't work!

As it is I am reading the b/w wire at the fuse box as being shorted to ground which I am pretty sure is not right and could explain the full reading on the gauge; is there anything else using this fuse? Everything else seems fully functional.

 

[morbias]

OK, a quick google tells me the sender should read 90 ohms when empty and 10 when full, so I guess my fuel sender has had it

The short to ground was probably my mistake somehow, at least I hope it was and it's not a secondary problem.

If anyone can confirm whether the diagram is wrong or not that would still help me out!

 

[Torby]

Before you replace the sender, make sure your tank isn't connected to ground, as that would cause the gauge to read full at all times.

 

[Rob Gaskin]

Before you replace the sender, make sure your tank isn't connected to ground, as that would cause the gauge to read full at all times.

Not sure about that, the sender circuit should be isolated from the tank body surely. I would also suspect that the tanks are grounded just by how they locate and are held in place. ??

Morbias, you may be correct about the grounded wire due to a fault (contact) along it's length. Have you disconnected the sender at the tank to see if it still gives the same reading?

Yep the wiring diag looks wrong i.e. colour swap through connector 3.

 

[morbias]

Yep, disconnected the sender and tested the wiring from the rear of the car to the front. Took the gauge out and dismantled half the car in the process!

Yeah, pretty sure the diagram is iffy, it made my brain hurt trying to work it out